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首页> 外文期刊>Process Biochemistry >Extracellular nuclease from a thermophile, Streptomyces thermonitrificans: production, purification and partial characterization of - double strand preferential - deoxyribonuclease activity
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Extracellular nuclease from a thermophile, Streptomyces thermonitrificans: production, purification and partial characterization of - double strand preferential - deoxyribonuclease activity

机译：嗜热链霉菌嗜热链霉菌的胞外核酸酶：-双链优先-脱氧核糖核酸酶活性的产生，纯化和部分表征

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摘要

A thermophilic strain of Streptomyces thermonitrificans produced high levels of extracellular nuclease (designated as nuclease Stn β) when grown on nutrient broth glucose medium. Maximal nuclease activity (51 U ml~(-1)) was obtained, in 40 h, when the culture was grown on modified NBG medium at 45℃. The enzyme was purified to homogeneity with an overall recovery of 5.6% and a specific activity of 10,833. The relative molecular mass of the purified enzyme, determined by gel filtration, was 22.4 kDa and it showed an obligate requirement for Mn~(2+) for activity. The optimum pH and temperature of nuclease Stn β were 8.0 and 45℃, respectively. The enzyme was inhibited by Mg~(2+), Co~(2+), Cu~(2+), Zn~(2+) and Hg~(2+), inorganic phosphate, pyrophosphate, dithiothreitol, β-mercaptoethanol, EDTA and NaCl. Nuclease Stn β was stable to high concentrations of urea and organic solvents but susceptible to low concentrations of SDS and guanidine hydrochloride. Nuclease Stn β is a multifunctional enzyme with substrate specificity in the order of dsDNA > ssDNA RNA. The end products of dsDNA hydrolysis were predominantly oligonucleotides (85-90%) and small amounts of 5′ mononucleotides (10-15%) suggesting an endo mode of action.
机译：当在营养肉汤葡萄糖培养基上生长时，嗜热链霉菌的嗜热菌株产生高水平的细胞外核酸酶（称为核酸酶Stnβ）。当培养物在修饰的NBG培养基上于45℃生长时，在40 h内可获得最大的核酸酶活性（51 U ml〜（-1））。该酶被纯化至均质，总回收率为5.6％，比活性为10,833。通过凝胶过滤测定的纯化酶的相对分子质量为22.4 kDa，显示对活性的Mn〜（2+）的专性要求。核酸酶Stnβ的最适pH和温度分别为8.0和45℃。该酶被Mg〜（2 +），Co〜（2 +），Cu〜（2 +），Zn〜（2+）和Hg〜（2+），无机磷酸盐，焦磷酸盐，二硫苏糖醇，β-巯基乙醇抑制，EDTA和NaCl。核酸酶Stnβ对高浓度的尿素和有机溶剂稳定，但对低浓度的SDS和盐酸胍敏感。核酸酶Stnβ是一种多功能酶，其底物特异性为dsDNA> ssDNA RNA。 dsDNA水解的最终产物主要是寡核苷酸（85-90％）和少量的5'单核苷酸（10-15％），表明其作用是内在的。

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